On the whole, men and women have similar nutritional needs. That said, men tend to need higher levels of nutrients (and calories) than women because they are usually larger. Women, on the other hand, need more iron and folate during their childbearing years.
But should men and women follow the same dietary advice about fats and carbohydrates?
Some research suggests that differences exist in how men’s and women’s bodies process dietary fat and carbohydrates, resulting in different levels of blood cholesterol. Research findings have been inconsistent and often hard to compare, but studies suggest the following:
A diet low in saturated fat and cholesterol benefits both sexes, but it may be more effective in men. This was seen, for instance, in a study from Tufts University of middle-aged and older people who were put on such a diet. Calories were not restricted, so no weight loss occurred. The men had a bigger drop in LDL (“bad”) cholesterol and triglycerides (fats in the blood), on average. In women, triglycerides actually tended to rise. A low-fat, high-carb diet can raise triglycerides in men, too, but some studies indicate this is more common in women.
A low-fat diet may reduce HDL (“good”) cholesterol—but less so in men than in women, according to a review from the University of Washington. This is a well-known drawback of a low-fat diet, which tends to lower both HDL and LDL cholesterol. To counter this, focus more on eating healthy (that is, unsaturated) fats, while limiting saturated fats and refined carbs.
Men appear to be less efficient than women at converting the omega-3 fats found in some plant foods (for example, alpha-linolenic acid, notably in walnuts, flaxseeds and canola oil) into the heart-healthy, longer-chain omega- 3 fats, like those found in fish, according to a review paper by a British researcher. Humans generally don't convert these fats efficiently, which is why it is important to eat fish and not just plant sources of omega-3s.
The bigger picture: Why might men and women react differently to the same diet? A woman’s body deals with nutrients somewhat differently because of the needs of childbearing. For instance, estrogen affects the formation of lipoproteins in the liver, notably HDL and LDL, which help transport cholesterol through the bloodstream. Estrogen also may affect triglycerides. Because estrogen levels drop after menopause, some of these differences are reduced, though not eliminated, in older women.
Keep in mind, however, that gender is less important than many other factors (notably genetic ones) in determining who’ll do well on various diets. As is often the case, the average difference between the sexes is smaller than the differences among many individuals of the same sex. Men may tend to do better on a moderately low-fat, high-carb diet, and women better on a diet higher in unsaturated fats (such as those in vegetable oils, nuts, and fish) but still low in saturated fat (mostly from animal products). The trick is to find the diet that works best for you.